feat(vcs): resizable Push dialog with collapsible repository groups (#407)

The Push dialog had a fixed size and listed every repository's outgoing commits flat. Dialog gains a resizable option (corner grip, clamped to the viewport, numeric width as the minimum), both Push dialogs use it with the commit list filling the body, and the multi-repository Push dialog shows each repository as a collapsible group (clicking the row still toggles its checkbox).

Fixes #397

Co-authored-by: a-rookie-of-C-language <[email protected]>

src/ui/Dialog.module.css

@@ -16,6 +16,7 @@
 .dialog {
   display: flex;
   flex-direction: column;
+  position: relative;
   max-width: 100%;
   max-height: 100%;
   background: var(--bg-dialog, var(--bg-elev));
@@ -36,6 +37,32 @@
   box-shadow: var(--shadow-popup);
 }
 
+/* Corner grip for `resizable` dialogs (over the footer's right padding). */
+.resizeGrip {
+  position: absolute;
+  right: 0;
+  bottom: 0;
+  width: 16px;
+  height: 16px;
+  cursor: nwse-resize;
+  touch-action: none;
+  background: linear-gradient(
+    135deg,
+    transparent 55%,
+    var(--fg-faint) 55%,
+    var(--fg-faint) 62%,
+    transparent 62%,
+    transparent 72%,
+    var(--fg-faint) 72%,
+    var(--fg-faint) 79%,
+    transparent 79%
+  );
+  opacity: 0.55;
+}
+.resizeGrip:hover {
+  opacity: 1;
+}
+
 /* Title bar (drag handle). macOS: traffic lights then the title; else title + close. */
 .titleBar {
   height: var(--h-dialog-titlebar, 32px);